XII] 



CIKRIPEDIA 



213 



by five calcareous plates, a right and left scutum, a right and 

 left tergum and a median carina, and in Balanus, the common 

 acorn-barnacle of our sea-shores, a further armour of triangular 

 plates develops in an additional outer fold of skin which encircles 

 the body. In Lepas, the barnacle which is usually found in clusters 



"3 



20 



Fio. 83. A view of Lepas anatifera, cut open longitudinally to show the dispo- 

 sition of the organs. From Leuckart and Nitsche, partly after Glaus. 



1. Stalk. 2. Carina. 3. Tergum. 4. Scutum. 5. 1st antennae. 

 6. Mandible with "palp" in front. 7. 1st maxilla. 8. 2nd maxilla. 

 9. The six pairs of biramous thoracic limbs. 10. Labrum. 11. Mouth. 

 12. Oesophagus. 13. Liver. 14. Intestine. 15. Anus. 16. Ovary. 

 17. Oviduct. 18. Testes. 19. Vas deferens. 20. Penis. 



21. Cement gland and duct. 22. Adductor scutorum muscle, which 

 closes the carapace. 23. Mantle cavity, i.e., the space intervening 



between the carapace and the body. 



on the bottom of ships, and which often seriously impedes their 

 progress, this ring is absent, but the anterior end of the head bearing 

 the first antennae at its end has grown out into a long stalk which 

 lodges some of the internal organs of the body. The second antennae 

 though present in the larvae are lost in the adult. The rest of the 



